1. Field of the Invention
The present invention relates to a film deposition apparatus and a substrate process apparatus for depositing a film on a substrate by carrying out plural cycles of supplying in turn at least two source gases to the substrate in order to form plural layers of a reaction product.
2. Description of the Related Art
As a film deposition technique in a semiconductor fabrication process, there has been known a so-called Atomic Layer Deposition (ALD) or Molecular Layer Deposition (MLD), in which a first reaction gas is adsorbed on a surface of a semiconductor wafer (referred to as a wafer hereinafter) and the like under vacuum and then a second reaction gas is adsorbed on the surface of the wafer in order to form one or more atomic or molecular layers through reaction of the first and the second reaction gases on the surface of the wafer, and such an alternating adsorption of the gases is repeated plural times, thereby depositing a film on the wafer. This technique is advantageous in that the film thickness can be controlled at higher accuracy by the number of times of alternately supplying the reaction gases, and in that the deposited film can have excellent uniformity over the wafer. Therefore, this deposition method is thought to be promising as a film deposition technique that can address further miniaturization of semiconductor devices.
Such a film deposition method may be preferably used, for example, for depositing a dielectric material to be used as a gate insulator. When silicon dioxide (SiO2) is deposited as the gate insulator, a bis (tertiary-butylamino) silane (BTBAS) gas or the like is used as a first reaction gas (source gas) and ozone gas or the like is used as a second gas (oxidation gas), for example.
In order to carry out such a deposition method, a single-wafer deposition apparatus having a vacuum chamber and a shower head at a top center portion inside the vacuum chamber and a deposition method using such an apparatus has been under consideration. When such a deposition chamber is used, it takes a long time to purge the reaction gases with a purge gas, resulting in an extremely long process time because the number of cycles may reach several hundred. Therefore, a deposition method and an apparatus that enable high throughput are desired.
Under these circumstances, the inventors of the present invention have investigated an apparatus in which plural wafers are placed on a turntable in a vacuum chamber along a rotation direction of the turntable and a film deposition is carried out while the turntable is being rotated, in order to improve throughput. Regarding such an apparatus, the following configurations have been proposed.
Patent Document 1 discloses a deposition apparatus whose process chamber has a shape of a flattened cylinder. The process chamber is divided into two half circle areas. Each area has an evacuation port provided to surround the area at the top portion of the corresponding area. In addition, the process chamber has a gas inlet port that introduces separation gas between the two areas along a diameter of the process chamber. With these configurations, while different reaction gases are supplied into the corresponding areas and evacuated from above by the corresponding evacuation ports, a turntable is rotated so that the wafers placed on the turntable can alternately pass through the two areas.
In this deposition apparatus, because the reaction gases and the separation gas are supplied in a downward direction and evacuated from the evacuation ports in an upward direction, particles in the chamber are blown upward by the gas flowing in the upward direction and fall onto the wafers, thereby contaminating the wafers.
Patent Document 2 discloses a process chamber having a wafer support member (rotation table) that holds plural wafers and that is horizontally rotatable, first and second gas ejection nozzles that are located at equal angular intervals along the rotation direction of the wafer support member and oppose the wafer support member, and purge nozzles located between the first and the second gas ejection nozzles. In addition, a vacuum evacuation apparatus is connected to a portion between the outer edge of the wafer support member and the inner wall of the process chamber. According to a process chamber so configured, the purge gas nozzles discharge purge gases to create a gas curtain, thereby impeding the first reaction gas and the second reaction gas from being mixed.
However, the gas curtain cannot completely prevent reaction gases from being mixed with each other but may allow one of the reaction gases to flow through the gas curtain to be mixed with the other reaction gas partly because the gases flow along the rotation direction due to the rotation of the wafer support member. In addition, the first (second) reaction gas discharged from the first (second) gas outlet nozzle may flow through the center portion of the wafer support member to meet the second (first) gas, because centrifugal force is not strongly applied to the gases in a vicinity of the center of the rotating wafer support member. Once the reaction gases are mixed in the chamber, an MLD (or ALD) mode film deposition can no longer be carried out as expected.
Patent Document 3 discloses a process chamber that is divided into plural process areas along the circumferential direction by plural partitions. Below the partitions, a circular rotatable susceptor on which plural wafers are placed is provided leaving a slight gap in relation to the partitions. In addition, at least one of the process areas serves as an evacuation chamber. In such a process chamber, process gas introduced into one of the process areas may diffuse into the adjacent process area through the gap below the partition, and be mixed with another process gas introduced into the adjacent process area. Moreover, the process gases may be mixed in the evacuation chamber, so that the wafer is exposed to the two process gases at the same time. When this happens, ALD (or MLD) mode deposition cannot be carried out in a proper manner in this process chamber.
Moreover, Patent Document 4 discloses a process chamber having a circular gas supplying plate divided into eight sector areas, four gas inlet ports for AsH3 gas, H2 gas, trimethyl gallium (TMG) gas, and H2 gas, respectively, the gas inlet ports being arranged at angular intervals of 90 degrees, evacuation ports that evacuate the process chamber and are located between the adjacent gas inlet ports, and a susceptor that holds plural wafers and is provided in order to oppose the gas supplying plate. However, Patent Document 4 does not provide any realistic measures to prevent two source gases (AsH3, TMG) from being mixed. Because of the lack of such measures, the two source gases may be mixed around the center of the susceptor and through the H2 gas inlet ports. Moreover, because the evacuation ports are located between the adjacent two gas inlet ports to evacuate the gases upward, particles are blown upward from the susceptor surface, which leads to wafer contamination.
Patent Document 5 discloses a process chamber having a circular plate that is divided into four quarters by partition walls and has four susceptors respectively provided in the four quarters, four injector pipes connected into a cross shape, and two evacuation ports located near the corresponding susceptors. In this process chamber, four wafers are mounted in the corresponding four susceptors, and the four injector pipes rotate around the center of the cross shape above the circular plate while ejecting a source gas, a purge gas, a reaction gas, and another purge gas, respectively. In such a process chamber, after one of the injector pipes passes over one of the quarters, this quarter cannot be purged by the purge gas in a short period of time. In addition, the reaction gas in one of the quarters can easily flow into an adjacent quarter. Therefore, it is difficult to perform an MLD (or ALD) mode film deposition.
Furthermore, Patent Document 6 (Patent Documents 7, 8) discloses a film deposition apparatus preferably used for an Atomic Layer CVD method that causes plural gases to be alternately adsorbed on a target (a wafer). In the apparatus, a susceptor that holds the wafer is rotated, while source gases and purge gases are supplied to the susceptor from above. Paragraphs 0023 through 0025 of the document describe partition walls that extend in a radial direction from a center of a chamber, and gas ejection holes that are formed in a bottom of the partition walls in order to supply the source gases or the purge gas to the susceptor, so that an inert gas as the purge gas ejected from the gas ejection holes produces a gas curtain. Regarding evacuation of the gases, paragraph 0058 of the document describes that the source gases are evacuated through an evacuation channel 30a, and the purge gases are evacuated through an evacuation channel 30b. With such a configuration, the source gases can flow into a purge gas compartment from source gas compartments located in both sides of the purge gas compartment and be mixed with each other in the purge gas compartment. As a result, a reaction product is generated in the purge gas compartment, which may cause particles to fall onto the wafer.
In the above configurations where plural wafers are placed on the turntable and the film deposition is carried out while rotating the turntable, there may be a problem in that it is difficult to control an adsorption time of the reaction gases and/or an oxidation time of the oxidation gas, while a relatively high throughput is kept. An appropriate adsorption time may vary depending on the reaction gases because some reaction gases are easily adsorbed and the others are not easily adsorbed on the wafer surface. In addition, an appropriate oxidation may vary depending on the oxidation gases because of variations in the oxidizing power. Moreover, the appropriate adsorption time and/or the oxidation time are different because of process conditions even when the same reaction gas (or oxidation gas) is used. Furthermore, not only two reaction gases but also three reaction gases may be used in some process of the ALD or MLD mode film deposition.
Under such circumstances, it may be convenient for the user of the ALD (MLD) film deposition apparatus to arbitrarily configure one apparatus in various ways depending on the reaction gases to be used, or in order to control the adsorption time of the reaction gases and/or oxidation gases. Therefore, an ALD (MLD) film deposition apparatus is desired that can offer a higher degree of freedom in designing in order to modify the apparatus depending on the processes. Unfortunately, the related art apparatus proposed in Patent Documents 1 through 5 can offer only a limited degree of freedom in changing the number of the reaction gases to be supplied into the chamber and controlling the adsorption time of the reaction gases, which in turn limits types of processes to be carried out in the apparatus.    Patent Document 1: U.S. Pat. No. 7,153,542 (FIGS. 6A, 6B)    Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2001-254181 (FIGS. 1, 2)    Patent Document 3: Japanese Patent Publication No. 3,144,664 (FIGS. 1, 2, claim 1)    Patent Document 4: Japanese Patent Application Laid-Open Publication No. H4-287912    Patent Document 5: U.S. Pat. No. 6,634,314    Patent Document 6: Japanese Patent Application Laid-Open Publication No. 2007-247066 (paragraphs 0023 through 0025, 0058, FIGS. 12 and 13)    Patent Document 7: U.S. Patent Publication No. 2007-218701    Patent Document 8: U.S. Patent Publication No. 2007-218702